1. Field of the Invention
This invention relates to a foldable bicycle that employs a minimum number of quick release clamps to lock the frames in the open position and additionally to adjust the seat tube height. Quick releases attached to collars joined to the top and bottom tubes secure both the front and back frame and the seat post position.
This invention also relates to a folding frame configuration having an in-line crank housing to permit the use of the standard method of attachment of the front Derailleur. The in-line configuration uses a front frame (mens or women's) collared onto a complete triangle back frame with a standard locking release clamps. The bottom collar is located below the crank housing.
In particular, in accordance with the first aspect of this invention the bicycle has rigid front and rear frames collared together with a unique locking device at the top.
2. Prior Art
The number of techniques to fold a strong frame collapsible bicycle have in the past determined the usefulness of the product, those with fewer steps being far more practical and marketable. Prior to this invention, many bicycles such as the DaHon, U.S. Pat. No. 4,067,589, involved many folding steps, one step always being to lower the seat tube during folding as a discreet operation. The present inventor in U.S. Pat. No. 4,448,437 defined a construction with a separate step to lower the seat tube but, with an overall simplified folding operation. A few bicycles such as the Bridgestone "Grandtech", U.S. Pat. No. 4,579,360 involved few steps but had to sacrifice the strength of the open bicycle by distorting the seat post to achieve the limited number of folding steps. However, even in this configuration, the seat tube still must be separately lowered. U.S. Pat. 4,448,437 established for the first time the concentric seat post technology as commercially viable and that patent is expressly incorporated herein by reference. Bicycles employing that basic geometry have been sold commercially for over ten years and represent a basic technological advancement in foldable bicycles.
A development of that basic technology is defined in U.S. Pat. No. 4,900,047 which employed a binder bolt mechanism to lock the foldable frames in a rigid open condition. Despite these improvements there still exists in the bicycle industry a need for a frame system that minimizes the number of components yet maintains the frame in a rigid and stable condition when opened, to provide a safe yet comfortable bicycle. In that regard the rigidness of the frame in the open condition ultimately determines the suitable of the bicycle as a riding system. consequently, the desire to provide increased utility by folding and to reduce components, to thereby reduce costs and mechanical problems, is contradictory to providing a rigid frame when in the open position. For example, Italian Pat. 26,352 illustrates a folding collared configuration however separate clamps are required to position the seat. Moreover, given the location of the crank, below the lower collar section, an undue stiff riding geometry exists due to the steep seat tube angle. Additionally, the rear frame cannot fold completely within the front frame thus, a compact design does not result.
Within this technology, the technique of providing complete folding or nesting has been to offset the crank housing. This permits the frames to nest but carries the difficulty of not being able to use standard attachment techniques for the front Derailleur. Additional attachment pieces have been necessary and the offset has required special adjustment of the chain guides which permit lateral movement of chain in that gear system.